1. Field of the Invention
The present invention relates to ink jet printing apparatus of the type using insertable print/cartridges and more specifically to printer interface constructions for high resolution printing with such print/cartridges.
2. Description of Background Art
There are known drop-on-demand ink jet printer systems in which a print head carriage bearing a print head traverses across the width of a print medium in a line printing operation. Between line printing sequences, the print medium is advanced to prepare for the next sequence. One useful approach for such printing systems is to construct the print head element as part of a disposable print/cartridge which contains an ink supply, drop-generating structures and electrical connections adapted for coupling to the printer, which provides drop-generating energy to such an inserted print/cartridge.
Heretofore, such insertable print/cartridges have been used one unit at a time in the printer and the resolution of the printing output has been dictated by the interspacing of orifices in the print/cartridge, e.g. 12 orifices per vertical character dimension. As described in U.S. patent application Ser. No. 855,302, entitled "Double Pass Printing in Dot Matrix Printer," filed Apr. 24, 1986, in the name of M. J. Piatt, the resolution of print output from such printers can be effectively doubled by employing a retrace line-print mode wherein the print media is advanced by one-half the vertical dot spacing after a first line printing pass. During return traverse of the carriage, a print output, e.g. of the 12 orifices, is interlaced between the forward line-print output so that the vertical resolution attained is doubled, e.g. to 24 pixels per nominal vertical character height. While this print output is quite adequate for producing highly legible text, it would be desirable for some applications, e.g. the printing of graphics ahd high quality text, to have the capability of a higher resolution of the orifices. Alternatively, such capability can be used to increase the overall output speed of the printer, i.e. allowing the printer to print a successive line of text during the retrace of the print carriage, rather than interlace.
There are several approaches which can be pursued to increase effective resolution of such print/cartridge printers. First, the resolution and number of the orifices in a print/cartridge can be increased, e.g. from 12 per character height to 24 or 48 per character height. Such orifice and drop generator densities present a difficult fabrication problem, particularly for print/cartridges that would be disposable after the ink supply is empty. In a second approach, more interlacing line retraces can be utilized, or a combination of line retracing and increased orifice density can be employed. However, line retracing itself is not without disadvantages and difficulties. Line retracing occurs at the cost of decreased throughput rate. Also, at high resolutions, it becomes more difficult to achieve the requisite accuracy of media advance for proper vertical alignment of the interlacing ink drops.